When Nasa wants to send a probe out to the edges of the solar system they often use a sort of gravity slingshot approach where they send the probe toward the inner planets and speed it up a lot by hitting their gravity fields from just the right angle as they're passing by.

Now, technically, the momentum imparted to the probe is momentum lost for the planets that sling shot it, but it kind of shows that you can transfer energy from one object to another one way, if you hit its gravitational field just right.

Do you think any similar types of effects might allow a black hole to transfer energy to surrounding objects without having to allow any actual particles or photons to escape from it?

August 28th, 2008, 04:53 AM

Harry Costas

G'day from the land of ozzzzzzzzzz

Kojax said

Do you think any similar types of effects might allow a black hole to transfer energy to surrounding objects without having to allow any actual particles or photons to escape from it?

Coincidences between Gravitational Wave Interferometers and High Energy Neutrino Telescopes

Authors: Thierry Pradier
(Submitted on 16 Jul 2008)

Quote:

Abstract: Sources of gravitational waves (GW) and emitters of high energy (HE) neutrinos both involve compact objects and matter moving at relativistic speeds. GW emission requires a departure from spherical symmetry, which is the case if clumps of matter are accreted around black holes or neutron stars, and ejected in relativistic jets, where neutrinos are believed to be produced. Both messengers interact weakly with the surrounding matter, hence point directly to the heart of the engines that power these emissions. Coincidences between GW interferometers (e.g. Virgo) and HE neutrino telescopes (e.g. Antares) would then give a unique insight on the physics of the most powerful objects in the Universe. The possibility, observability and detectability for such GW/HE neutrino coincidences are analysed.

August 28th, 2008, 07:15 AM

sak

Newton’s law states that "A particle will stay at rest or continue at a constant velocity unless acted upon by an external unbalanced force, The rate of change of momentum of a body is proportional to the force acting on the body and is in the same direction.”
My understanding on this:
Gravitational field pulls an object allowing it to gain momentum, but the momentum gained will be equal to the momentum required to escape from the gravitational field.
I think, in theory we get/ need same amount of energy to lower/ rise 1 Kg to 1m.
Intrested to listsen.

“If a spacecraft gets close to the Schwarzschild radius of a black hole (the ultimate gravity well), space becomes so curved that slingshot orbits require more energy to escape than the energy that could be added by the black hole's motion.
A rotating black hole might provide additional assistance, if its spin axis points the right way. General relativity predicts that a large spinning mass produces frame-dragging — close to the object, space itself is dragged around in the direction of the spin. In theory an ordinary star produces this effect, although attempts to measure it around the sun have produced no clear results. General relativity predicts that a spinning black hole is surrounded by a region of space, called the ergosphere, within which standing still (with respect to the black hole's spin) is impossible, because space itself is dragged at the speed of light in the same direction as the black hole's spin. The Penrose process may offer a way to gain energy from the ergosphere, although it would require the spaceship to dump some "ballast" into the black hole, and the spaceship would have had to expend energy to carry the "ballast" to the black hole”

August 28th, 2008, 02:50 PM

kojax

Wow. These are very interesting replies. I want to be clear about what I was suggesting, though:

I was curious whether the bh's gravity could impart energy to objects outside its event horizon too.

August 28th, 2008, 03:08 PM

Scifor Refugee

Quote:

Originally Posted by kojax

Wow. These are very interesting replies. I want to be clear about what I was suggesting, though:

I was curious whether the bh's gravity could impart energy to objects outside its event horizon too.

It can turn potential energy into kinetic energy, sure. Any time an object falls toward a black hole (or a planet, or whatever) it is gaining kinetic energy because of the gravity. It doesn't matter if you're inside or outside the event horizon.

August 28th, 2008, 06:17 PM

Harry Costas

G'day from the land of ozzzzzzz

Kojax got the big WOW!!!!!!!

You said

Quote:

I was curious whether the bh's gravity could impart energy to objects outside its event horizon too.

Some kids come onto the site with their words and express a bit of down under ha ha.

In way Solomon in his short wisdom, said

Quote:

Come on stop the black hole crap allready!

Black hole in their true definition with a singularity do not exist.

So that knocked the crap out of that.

Black holes with extreme ultra compact matter may create an event horizon in theory. THis has not been observed.

September 1st, 2008, 01:49 AM

kojax

So I'm wondering some more: Once the repulsive force is too weak to cause any motion by pushing outward (because the force pulling inward is too strong), would it start pushing sideways?

Do you think it would make the black hole spin? And, I also wonder if it would align so that it was always spinning the same direction, or if it would periodically spin one direction and then the other. (So that conservation of angular momentum was observed, even though the energy is causing motion)

September 1st, 2008, 03:51 AM

Harry Costas

G'day from the land of ozzzzz

The make up of the compact matter within a black hole whether it be quarks or preon particles or maybe just Neutron merging forming an extreme compaction or maybe a composite will determine its properties.

We do know its a plasma and from that we can determine some properties.

The plasma universe consists of swirling streams of electrons and ions flowing in filaments which tend to corkscrew or spiral. They self pinch from the magnetic fields that they generate around themselves.

There is a tendency for these filaments to repel at close range, and attract at greater distances. However, when in close proximity they may also spiral around one another. When this happens there is also a tendency for the filaments to compress between them any material (ionized or not) in the plasma. This is called the Z-pinch effect.

Z-pinch experiments have shown the Production of Neutrons and their compaction and the formation of very fast jets.

This maybe a key to the workings and formation of jets in compacted matter such as Neutron Stars and the so called black holes.

September 1st, 2008, 12:52 PM

kojax

These jets are very interesting. Where would I go to read the basics about them, since I hadn't heard of them before?

September 1st, 2008, 01:41 PM

Gijs

Re: Could a black hole transfer energy from its gravity?

Quote:

Originally Posted by kojax

Now, technically, the momentum imparted to the probe is momentum lost for the planets that sling shot it.

That is not necessarily so. Because if the radius to the planet is bigger when your space ship is floating in the direction of the orbit of the planet around the sun then when your ship is behind the planet, the momentum of the planet will actually increase. This is because the energy needed for the acceleration of the space ship is gotten from the energy of it`s mass.
Because gravity slows time and therefore relatively slows light, the energy of the mass of the ship according to E=MC^2 is less in regions close to the planet. Where must that energy go as the ship gets closer to the planet? The awnser everybody knows: it is converted into kinetic energy. Of course this is the relativistic few and not the newtonian.